Won't start when hot

[claybags]

Just when I'm ready for final DMV inspection!!! Ran for about 6 min, then quit and would not restart! OK, I tow it home(only a mile away) put 9 gallons of fuel in and waited until the next AM. Started right up so I ran for another couple of hot laps around the block- about 8 miles- and parked in the garage and thought hmmm, musta' been MT tanks. Wouldn't start 1/2 hour later- or all the rest of the day. Day 3, fill the tanks full, undo feed line to fuel rail, pumps out approx. 1 cup of fuel and stops pumping. Hook line back up nd she fired right up. Let it idle , water temp up to about 160, and it quits. Wouldn't start again. Soooo- ant thoughts as to what is going on? History- car has been in the build stage for 6 years. I've run it every month or so, put some fuel stabilizer in the tank. Never any problems. New filter/regulator on the way. Changed the fuel pump relay. Why does the pump just stop running. Does it get sleepy like me? At this point, I REALLY don't want to change the pump! Is it possible in any way to connect an external pump to the pressure feed line out of the tank pulling fuel thru the internal pump? (I didn't think so, but hope springs eternal) Any thoughts greatly appreciated. Oh yeah, it's an LS6 with upgraded cam, etc. My wideband o2 sensor reads good air/fuel ratio also- when the thing runs...…..

Cheers Jeff

[crash]

I would start by putting a gauge on the fuel rail and seeing what it does. If the pump cuts out, then measure voltage and see if it is a pump problem or a computer command issue. If computer command, did you get the ECU flashed? Was it done by FFR? Could it be that VATS is still engaging?

[claybags]

Crash, good pressure at the fuel rail when pumping. Ecu was flashed originally by FFR, then checked with HP tuner and VATS eliminated. Pump seems to run fine when running. To me, it sounds like an ECU command? When cold and ignition turned on, you can hear the relay click and pump run. When hot, relay clicks but pump does not run.
Thanks, Jeff

[Roger Reid]

Chinese copy of a Bosch fuel pump? Lots of them around.

[claybags]

This is the original pump from my 2000 donor. Maybe like some of us, it's just old. LOL
Jeff

[VRaptor SpeedWorks, LLC]

Crash, good pressure at the fuel rail when pumping. Ecu was flashed originally by FFR, then checked with HP tuner and VATS eliminated. Pump seems to run fine when running. To me, it sounds like an ECU command? When cold and ignition turned on, you can hear the relay click and pump run. When hot, relay clicks but pump does not run.
Thanks, Jeff

Is this the factory in-tank OEM pump? That last bold part above should be the biggest clue, I think. If the relay clicks but the pump doesn't run....and you've already replaced the relay....about the only thing left to check is if you have power and ground right at the fuel pump connector on the tank when the relay is engaged but the pump is not running. If you have power and ground to the pump and the pump is not running.....you have a bad pump. If you're missing power or ground to the pump connector, then you have an issue with the wiring somewhere.....either the replacement relay is also bad (unlikely unless it was also used), or the relay is not getting power to send thru to the pump....or the wire between the relay and fuel pump connector is broken...or you have bad ground to the pump.

[VRaptor SpeedWorks, LLC]

Are your fuel tanks vented so that air can get into the tanks so the tanks are not creating a vacuum inside....preventing the pump from pumping fuel?

[claybags]

Well, I think problem solved. Had to remove some of the aluminum around that area behind the tank to get better access to wiring, plumbing and such. That was a good thing as now that area is removable and provides great access for the future! Now the GOOD part- Had a loose wire connection aaaand another faulty pump relay. Replaced that and so far so good. Starts every time - hot, cold, or indifferent. Mama told me it's always the easiest solution. Thanks Mom and to all who contributed some info and suggestions. Oh yeah- Shane, the tanks are vented.

Cheers, Jeff